Hey there,
1) A battle ends immediately when the last threat is destroyed.
2) Yes, all location features (pits, obstacles, difficult terrain) can be bypassed with hover.
3) Most churn etc. make allowances for how location features change or are added, otherwise it is up to you to judge.
4) The way I interpret threat movements is to always move them into spaces that are most advantageous. A certain amount of player interpretation is needed.
My experience was very different than yours, which is as expected. For example I like experimenting with different equipment when I get it and having a mix of different ranged and melee weapons. Other players find one build and they stick with it throughout the whole game.